best molded thread form for low friction 1

[mrPelagic]

Hello!
I am looking to position something with molded threads. it's small, low load. I'd like minimum friction.
Since I am molding the threads, I have some freedom. backlash is not a big issue.

I am thinking buttress- type threads will give less friction than acme or others. it will be a very steep, 3 start thread, so the goal is back-drivability, and low stroke. regardless, I will likely make them "stub" threads.

thanks for your thoughts.

 

[GregLocock]

I agree. My guess is that a 90 degree flank angle, ie a square thread, with a large amount of clearance, will have the lowest friction. You might need to get clever and actually go for a negative angle, so that under load the form deflects to give constant surface pressure and no wedging.



Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[MikeHalloran]

A bigger consideration is the parting line.
Consider using a double-D shape, so the parting line mismatch doesn't get near a sliding surface.


Mike Halloran
Pembroke Pines, FL, USA

 

[GregLocock]

Ah, yes, I think I see. Mike, how does that reduce the effect of the parting lines? OP, how are you forming the female thread?

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[MikeHalloran]

The double-D recommendstion most usefully applies to male tbreads.

For female threads, interrupted threads may be useful, but flash removal can be a problem.
It may be useful to mold around a polished male threaded core and spin it out.

Mike Halloran
Pembroke Pines, FL, USA